1. Field of the Invention.
My invention relates to nursing bottles, and more particularly to nursing bottles of the type which comprise a thin-walled shell which, during nursing, encloses a flaccid liner containing infant formula.
2. Description of the Prior Art.
In a conventional nursing bottle having rigid side walls both formula and air are present and are thus ingested by the feeding infant, which feels discomfort and distress to the presence of air in its stomach. The development of nursing bottles comprising thin-walled shells adapted to enclose a flexible liner which functions as the formula container was intended to alleviate if not completely eliminate the problem of air ingestion.
It was believed that as formula was drawn from the flexible liner the side walls of the liner would collapse about the remaining formula, thereby avoiding the creation of a partial vacuum within the bottle such as occurs in those bottles having rigid sides. It has been determined, however, that air will still be drawn into a nursing bottle having a flexible liner, especially after the contents are partially drawn out and the bottle is turned upright. Although the side walls of the liner do collapse, the tension exerted on the side walls by the weight of the formula at the bottom of the liner tends to separate the collapsed side walls, which generates a partial vacuum within the liner that draws air.
In response to this continuing problem, various devices have been developed to expel air from nursing bottles having flaccid liners Such devices will be called "expellers" herein.
These prior art expellers, however well adapted to the task of expelling air from the flexible liner, constitute one more item which must be carried by the mother, along with additional liners, powered formula, additional nipples, etc.; in addition, of course, to the nursing bottle shell and its associated cap.
Related Art. It is believed that the documents listed immediately below contain information which is or might be considered to be material to the examination of this patent application.
______________________________________ Patent No. Inventor ______________________________________ 3,648,873 S. Grobbel 3,955,698 H. Hammer 3,998,348 M. Sammaritano 4,339,046 R. Coen 4,401,224 F. Alonso 4,796,767 F. McKeown 4,821,896 P. Cheng ______________________________________
The term "prior art" as used herein or in any statement made by or on behalf of applicant means only that any document or thing referred to as prior art bears, directly or inferentially, a date which is earlier than the effective filing date hereof.